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Provisional designations for interstellar objects will be handled using the C/ or A/ prefix (as appropriate), with the designation using the comet system.

Accordingly, the object A/2017 U1 receives the permanent designation 1I and the name 'Oumuamua. The name, which was chosen by the Pan-STARRS team, is of Hawaiian origin and reflects the way this object is like a scout or messenger sent from the distant past to reach out to us ('ou means reach out for, and mua, with the second mua placing emphasis, means first, in advance of).

This first interstellar object is being handled as a special case. A small committee of the WGSBN will be created to codify the circumstances under which an object will quality for an I-number and the rules that will apply to the names, bearing in mind the precedent set by this case. A formal report will follow their deliberations.

One week after the discovery, asteroid hunter Luca Buzzi tracked ʻOumuamua from northern Italy with a 50-minute image exposure on October 26. In an email, Buzzi said he fought thin cirrus clouds to barely pull the asteroid above the visual threshold using his 0.84-meter telescope and Planetary Society-funded CCD camera. He ordinarily uses the equipment to track potentially hazardous near-Earth asteroids.

The name has been a source of comment and complaint on the Minor Planet Mailing List.

First, a number of posters wondered about the diacritical mark at the beginning of the name, mainly because it might cause problems with alphabetical sorting and searching. In the Hawaiian language, the mark is technically an 'okina, which indicates a glottal stop. See...

Per Dave Tholen, an astronomer with the Institute for Astrophysics, University of Hawai'i, the new name is pronounced: owe moo-uh moo-uh

Second, and perhaps a greater problem, is the use of an uppercase "i" to indicate "Interstellar" in the designation, in this case "1I." The problem is that it can easily be confused with the number "1," a lowercase "L" or an uppercase letter "i" depending on the typeface. There was a suggestion that they should have used a less-confusing uppercase "E" to indicate "Extrasolar."

We suggest that A/2017 U1 formed in a protoplanetary disk in the Carina/Columba associations and was ejected by a planet ≈40 Myr ago. The absence of ice indicates an origin inside the “ice line” of the disk plus an ejection velocity of 1-2 km sec−1 (assuming the cluster was already unbound), constrain the mass mP and semi-major axis aP of the planet.

The discovery of 1I/2017 U1 ('Oumuamua) has provided the first glimpse of a planetesimal born in another planetary system. This interloper exhibits a variable colour, within a range that is broadly consistent with local small bodies such as the P/D type asteroids, Jupiter Trojans, and dynamically excited Kuiper Belt Objects. 1I/'Oumuamua appears unusually elongated in shape, with an axial ratio exceeding 5:1. Rotation period estimates are inconsistent and varied, with reported values between 6.9 and 8.3 hours. Here we analyse all reliable optical photometry reported to date. No single rotation period can explain the exhibited brightness variations. Rather, 1I/'Oumuamua appears to be in an excited rotational state undergoing Non-Principal Axis (NPA) rotation, or tumbling. A satisfactory solution has apparent lightcurve frequencies of 0.135 and 0.126 hr-1 and implies a longest-to-shortest axis ratio of 5:1, though the available data are insufficient to uniquely constrain the true frequencies and shape. Assuming a body that responds to NPA rotation in a similar manner to Solar System asteroids and comets, the timescale to damp 1I/'Oumuamua's tumbling is at least a billion years. 1I/'Oumuamua was likely set tumbling within its parent planetary system, and will remain tumbling well after it has left ours.

I’ll bet this is actually referring to the observation of 1I/‘Oumuamua that’s listed on MPEC W75, and one of the automated routines at the MPC didn’t interpret the designation correctly.

Sincerely,Alan [Hale, of Comet Hale-Bopp fame]

Although magnitude 24.3 is dim, it's about 4 to 5 magnitudes brighter than one would expect for 1P/Halley at this time as it nears aphelion. Hence the original puzzlement about the magnitude. The error has evidently been recognized. If you follow the link to the MPC page, 1P/Halley is no longer present.

The bureaucrats at Pan-STARRS and the IAU have created quite a mess by not keeping things simple and by embracing cultural outreach. Good for job security, I suppose; correcting the problems gives them something to do.

A constructive comment about the excessively large pictures you've been posting recently. They really mess up the page they're on and they're also hard to see. The current picture of 'Oumuamua's track you posted is 4986 x 4674 pixels and required extensive scrolling to see all of it on my screen, or setting the browser window at 30% to see all of it at once.

For the attached version here, I reduced the size to 1200 x 1125 pixels, which better fits the window (I didn't have to scroll the preview on my screen to see it all) while still leaving most details legible. If necessary, you could include a link to the original full-size picture to see the finest details. In this case...

BTW, the spiraling path is reminiscent of comets coming from a distance. The movement forming the loops is caused by parallax as viewed from opposite sides of the earth's orbit over the course of a year. For example, look at the path of comet C/2017 O1 (ASASSN) on Seiichi Yoshida's page...

Today in the journal Nature Astronomy, astronomers report observations that suggest 'Oumuamua is encased in a dry, carbon-rich crust that could have protected a water-ice core from being vaporized as it made a close pass of our sun earlier this year. You can almost think of it as the hull of a spaceship.

"We've discovered that this is a planetesimal with a well-baked crust that looks a lot like the tiniest worlds in the outer regions of our solar system, has a greyish/red surface and is highly elongated, probably about the size and shape of the Gherkin skyscraper in London.

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